Space discharge type harmonic generator



Sept. 7, 1943. J. MARKOWITZ 2,329,069

SPACE DISCHARGE TYPE HARMONIC GENERATOR Filed March 31, 1942 yum/11m?Patented Sept. 7, 1943 OFFICE :sPAoE mscnAnoE: TYPE HARMONIC VGENERATORJerome Markowitz, Allentown, Pa. Application'March 31, 1942, Serial No.436,946

3 Claims.- (01. 250--36) This invention relates to ocillating spacedischarge devices and has particular reference to their use as harmonicgenerators and for. the simultaneous production of many differentfrequencies.

One object of the invention is to provide an improved generator capableof oscillating at a.

number of related frequencies atthe same time. Another object of theinvention is to provide a, simple space discharge type oscillationgenerat'or which will produce a considerable amount of outputoscillation energy at harmonic frequencies far removed from thefundemental as for instance the 20th or even higher harmonics. Anotherobject of the invention is to provide an oscillation generator whichwill efficiently produce output oscillating energy simultaneously at aseries of related frequencies and without the use of external filterforwavetrap circuits.

Another object of the invention is the simultaneous production of anumber of related frequencies with equal ease at either audio or radiofrequency. 7 Other objects and advantages of the invention will becomeapparent as the specification proceeds. Y With the aforesaid objects inView, the invention consists in the novel combinations and arrangementsof parts hereinafter described in their preferred embodimenta'pointedout in the sub'joined claims, and illustrated in the annexed drawing.wherein like parts are designated by the same reference charactersthroughout the figure.

'In the drawing:

The figure shows) a space discharge oscillation generator embodying theharmonic generating feature of the invention.

The advantages of theinvention as here outlined are'best realized whenall of its features and instrumentalities are combined in one and thesame structure, but'usefuldevices may be produced embodying less thanthewhole.

It Will be obvious to those skilled in the art to which the inventionappertains, that the same may be incorporated in several differentconstructions. The accompanying drawing, therefore, is submitted merelyas showing the preferred exemplification of the invention.

Generally "described the invention provides a harmonic generatorconsisting of a space discharge device oscillating at a givenfundamental frequency and a second space discharge device coupled to itwhich produces output oscillating energy at a harmonic frequency orsimultaneously at a number of harmonic frequencies depending uponcertain circuit constants.

The fundamental frequency could more aptly be termed, a differencefrequency as (the differential betweenfrequencies of a series ofresultant harmonics would be determined naturally by that of thefundamental. The oscillator for producing this difference frequencyconsists of a space discharge device in combination with componentswhich may form the circuit .of a Hartley. The space'discharge device maybe of the indirectly heated cathode type. Connected to the grid is aninductance. The cathode is connected to an intermediate point on thisinductance coil. Plate voltage to the oscillator is applied through asecond inductance. This inductance is peaked preferably at a lowerfrequency than the difference frequency. Output oscillatory energy isobtained from the grid end of the inductance and is coupled to thecontrol grid of a second space discharge device. This space dischargedevice consists of a cathode, anode, control grid and a. secondary grid.A high grid bias is applied to this space discharge device in anyconvenient manner. A positive potential is applied to the second grid.This potential is derived from the plate of. the difference frequencyoscillator and by virtue of this fact this potential varies inaccordance with the frequency of the differential oscillator. In otherwords the secondary grid may be considered to be modulatedat thedifference frequency. The anode of the second space discharge device isalsomodulated at the'difi'erence frequency by voltage secured from theanode of the difference frequency oscillator. However this voltage isap,-' plied thru an inductance which is tuned to the desired harmonicfrequency. If a sequence of several of the harmonic frequencies isdesired this inductance is designed to have a fiat resonance peak. It ispossible to efficiently secure I relatively large amounts of oscillatingenergy simultaneously at a number of harmonics as for instance the 20thto the 30th inclusive. Referring in detail to the drawing: The figuredenotes a preferred embodiment-of the invention. The same may include aspace discharge device l including a cathode, anode, heater and grid,Connected to the grid 4 is a usual bias combinationconsisting of.parallel connected condenser I and resistor B. One end of an inductance8 is connected to the grid .4 thru the aforementioned bias combination.The cathode 3 of the space discharge device is connected to anintermediate point on the inan inductance l2.

ductance 8 as shown at point iii. The remaining terminal of inductance 8is connected to a common ground as shown at 23. The heater terminals Xare connected to an appropriate source of current Y. Plate voltage foranode is obtained from a source of potential ll thru The second spacedischarge device l3 includes a cathode, anode, control grid, a secondarygrid and a heater. The heater terminals X are connected to anappropriate source of current Y. The cathode I5 is connected to thecommon ground as shown. The control grid [4 is biased by a resistor 2|connected between said grid and ground. This grid is excited by anoscillating current which is generated by space discharge device I. Thecoupling is performed by a condenser 22 connected between grids 4 andHi. The secondary grid I! is modulated by an oscillating potential whichis derived from the anode 5 of space discharge device I. An inductanceI9 is connected between the anode l8 and the secondary grid I! of spacedischarge device l3. A tuning condenser may be connected in parallelwith this inductance. A tuning condenser 9 may also be connected inparallel with inductance 8. Harmonic output oscillation energy may beobtained from the space discharge device l3 by means of a line 24connected to a load 25 which may be returned to ground as shown.Condenser 28 is a small by-pass to the common ground which prevents theharmonic oscillating energy from leaking back thru inductance l2. Thesize of condenser 28 is such that it offers a low impedance path toenergy of the harmonic frequency but high impedance to oscillatingenergy of the fundamental frequency.

A typical example of the operation of the invention would be as follows:Space discharge device I is caused to oscillate at a frequency of 50,000cycles by means of the proper value of inductance 8 and condenser 9. Ifone wished to cover at kilocycle intervals a band of a frequency of 800to 1200 kilocycles it wouldbe necessary to generate the 16, 17, 18, 19,20, 21, 22, 23 and 24th harmonics inclusive. In this case inductance l9would be made broadly resonant, a feature which could be accomplishedsimply by using a relatively high resistance inductance I9. Thisinductance would be peaked at about 9'75 kilocycles. Variable tuningcondensers 9 and 20 would be used to tune to an exact given fundamentalfrequency and harmonic. In cases where a single harmonic frequency isdesired a high ratio of capacity to inductance is used, in accordancewith the well known rule concerning inductance and capacity and.sharpness of resonance. Where a band of frequencies are to be coveredthe amount of capacity is reduced or it is omitted entirely.

I am aware of the fact that previously it was well known that high bias,high excitation and broadly tuned resonant circuits were conducive tothe production of harmonics by space discharge repeating devices,however, in these circuits the harmonic energy and plate efficiencydrops ofi rapidly as, the harmonic sequence progresses whereas with thepresent invention large amounts of harmonic energy can be secured withrelatively good plate efliciency and without the use of extra filters orwavetrap circuits.

Having thus described my invention what I claim is:

1. A harmonic generator comprising a given frequency oscillatorconsisting of a space discharge device having a cathode, anode and grid,one end of an inductance connected to said control grid, an intermediatepoint of said inductance connected to said cathode and a connection fromthe other end of said inductance to the negative terminal of a source ofanode potential and means for connecting the positive terminal of saidanode potential source to said anode through an inductance wherebyoscillations are produced, a second space discharge device having acathode, anode, control grid and secondary grid and a coupling condenserconnected between the control grids of the first and second mentionedspace discharge devices, a connection from the anode of the firstmentioned space discharge device to the secondary grid and also aconnection from the anode of the first mentioned space discharge deviceto the anode of the second mentioned space discharge device thru aninductance whereby a harmonic series of oscillation energywill flow thruthis coil whose frequencies will depend upon its inductance.

2. A harmonic generator comprising a given frequency oscillatorconsisting of a space discharge device having a cathode, anode and grid,an inductance connected between said anode and grid, a connection fromsaid cathode to an intermediate point on said inductance, means forapplying between said cathode and anode a voltage sufficient to causeoscillation and means for coupling output oscillating energy from thegrid of the said space discharge device to the control grid of a secondspace discharge device having a cathode, anode, control grid and sec-.

ondary grid,'and means for supplying the secondary grid of said secondspace discharge device with a potential modulated at the oscillationfrequency of said given frequency oscillator and an inductive meansconnected between the anode and secondary grid of said second spacedischarge device whereby the potential applied to thesecondary grid willalso be applied to the anode but through said'inductive means andwhereby a harmonic or series of harmonic frequencies will be generatedwhose frequency or frequencies will be dependent on the inductance ofsaid inductive means.

3. A harmonic generator comprising a given frequency oscillatorincluding a space discharge device having a cathode, anode, and grid anda space discharge repeater device, said repeater device having acathode, anode, control grid and a secondary grid, means for excitingthe control grid of said repeater device with oscillating energy derivedfrom the grid of said given frequency oscillator space discharge device,and means for applying to the secondary grid of said repeater device amodulated potential varied by the given frequency oscillator and aninductance means tuned to a harmonic of the given frequencyoscillator-connected between the anode and secondary grid of saidrepeaterdevice where by oscillating energy will be set up in saidinductance means whose frequency-will be harmonic to, that of the givenfrequency oscillator;

JEROME MARKOWITZ.

